Compass-ruler.



J. A. RYDMAN.

COMPASS RULER.

APPLIoATIoN FILED APR. 1, 190s,

932,907, v Patented Aug. 31, 1909.

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JOHN ARTHUR RYDMAN, F FRUITVALE, CALIFORNIA.

COMPASS-RULER.

Specification of Letters Patent.

Application filed. April 1, 1908. Serial No.'424,61f1.

To all whom it may concern:

lie vit known that l, JOHN ARTHUR Ern- NAN, :i citizen ot the United States, residing at ifrnitvale, in county ot Alameda and Siate ot California, have invented a new and useful Vimprovement in Compass-Rulers, ot' which the Yfollowing is a specification in such 'tuil and clear terms as will enable those skilled in the art to construct and use the saine.

lily invention relates to the art of laying ott and reading ships courses and bearings on charts, and has i'or its object to provide ne i and improved means tor laying otl` and reading courses. To understand its relation to the prior art it is to be borne in mind that directions on the earth are expressed in relation to a true north, and also in terms ot a magnetic north, which varies in diii'erent legrces from the true north at different points on the earths surface. Charts used in navigation have lines running to the true north and south, and to the true east and west, and at various positions on their surr'aces, prints ot compass cards showing the variation ot the magnetic north trom the true north at the indi lated point on the ear-this snri'ace. To lay oil' a course on the chart it is required at present to correlate the chosen course with the directions on one of these compass cards by means otl parallel rulers moved step by step over the surface oit the chart between the point making the shi ps position, and one ot the compass cards. 'ihe operation is a diiiicult one on a rolling ship, as it demands that each ot the parallel rules shall be maintained constant in direction at all times, as the rules are alternately advanced.

i attain my objects by the means illustrated in the accompanying drawing of which- Figure 1 is a plan view of my compass ruler with part ot upper disk broken away; Fig. 2, a iongitudinal vertical, sectional view thereof, Fig'. 3, an end view of one of the legs; Fig. d is a view of one ot the disks marked with the points of the compass.

The saine numeral ot reference marks the same part throughout the various views.

My invention broadly expressed, consists in providing means for readily laying 0E or reading acourse on such a chart, not by establishing a direct relation between it and one ot the aforesaid compass cards, but by establishing a direct relation between it and one ot the true north and south lines or one ot the true east and west lines thereon.

Vit also consists in providing means tor expressing directly the required course in terms ot Aboth the true north and the magnetic north.

lt also consists in providing means tor showing readily the required course in terms of the ships compass as modified by the deviation due to local magnetic conditions.

t also consists in the constructions, conbinations and arrangements hereinafter described and particularly pointed out in the claims.

1 provide two legs 1, 2, each ot these legs terminates in a circular disk 4, 5, said disks being concentric with each other, and turning on a pivo-t at 10. rlhe surface ot disk fl is marked off into marks indicating circular arcs, as degrees or compass points. Fig. 1 shows the preferable marking, which is into degrees in two series in reverse order, and the degrees marked 0H into quadrants; whereby it shows four quadrants ot O to 90 degrees, each ot the marks being double, as 60 in one series being 8O in the other, 90 in one series being 0 in the other. The O ot one ot these quadrants is set accurately to the line 6, which marks the junction ot the legs l and 2, and permanently fixed in that position.

Disk L1 is provided with a boss 7 and around this boss, and concentric with disks t, and 5 is a disk 8, smaller than disk 4, and exposing the marks aroundthe edge thereoi", disk 8 bearing on its surface the markings ot the mariners compass. A thumb nut 9 screws downward on boss 7, and by means ot screw 10 and head 11, locks the legs 1, and 2 in any angle.v Above disk v8 l provide a revoluble pointer 12, the use of which is to mark the deviation of the needle on the disk 8. Plates 13, and 14, and thumb nuts 15, and 16, are provided to secure disk 8 in any desired position with relation to either leg, and thumb nut 9 being somewhat larger than the boss prevents pointer 12, and disk 8, from coming oil.

Along the edges ot legs 1, and 2,'are divisions spaced ott' twenty to the inch, which are used tor measuring distances on a chart. it willbe noted that the lines marking these divisions are at right angles to the edges of the rules, and that any point as 17, has a corresponding point 1S on the opposite edge of the rule, said points being situated at Patented Aue. 31, 1909.

the extremities of imaginary straight lines drawn at right angles to the straight edges ot the rules. The utility of the above-described arrangement will appear in the following description ot' how my compass ruler is operated.

There are two ways of using my device; one with, and one without disk 8. The course being chosen, leg 2, is turned in the direction and to the point on disk A marking that course. The proper allowance. being made for magnetic variation. Leg l, is then set to one of the north and south lines on the chart and leg Q made to pass through the point marking the ships position; whereupon a line drawn along the leg-s straight edge marks the course on the chart. One of the east and west lines of the chart may be used instead of the north and south line, as a datum line for leg. The above-described mode oi' using my device will be used by some navigators who may prefer to do the little arithmetical calculations required rather than use the disk 8. But many will use disk 8 in preference, and in using my device with disk 8, the operation is as follows: The course being chosen, say NMI. or 45 degrees to the left of the junction line 6, and the magnetic variation being known say 2O degrees east, disk S is turned to the right until its Zero point coincides with 2O degrees on the scale of disk fl. In this position disk 8 is clamped by thumb nut 15, and leg 2 is revolved until its edge along line 6 coincides with the northwest point on disk et, which now makes an angle of G5 degrees with the true north point on disk 8, and clamped by thumb nut 9. This gives both the true and the magnetic course, reading on both scales; and if' leg l, is adjusted to a north and south line on the chart, the true and the magnetic course can be laid vott' by drawing one line along leg 2. But the sailing directions along this line have to be modified for the deviation of the compass due to local magnetic conditions. The amount of this deviation is experimentally determined in ways that need not be specified. Being known, the deviation is marked by the pointer 1Q. Suppose the deviation to be l0 degrees east, then the pointer is set to l() degrees to the left of the magnetic course on card 8, and clamped by thumb nut 9, which makes the sailing course for a true north westerly course 75 degrees west of the north point on the ships compass card. TWhere it is dif'licult to set my device to a true north and south line, leg l may be set to any east and west line of said chart so that said line passes through a division mark on one edge of the leg and the corresponding division mark on the opposite edge of said leg; and said marks being at right angles with said edges, said edges must indicate a north and south direction. The equal divisions on the legs l, and 2 are usable to measure distances as scaled on a chart, by comparing the distances as shown on said leg with the scale.

Having described my invention what I claim as new and desire to secure by Letters Patent of the United States is,

l. A compass ruler comprising an upper circular disk having marks indicating circular divisions, a lower circular disk concentric therewith said disks being pivoted at their centers, a compass card smaller than the said upper circular disk, superposed thereon, and revoluble about said centers, a leg extending from each of said disks, and means for clamping said disks in any angular position of said legs.

2. A compass ruler comprising an upper circular disk having marks indicating circular divisions, a lower circular disk concentric therewith, said disks being pivoted at their centers, a compass card smaller than the said upper circular disk, superposed thereon and revoluble about said centers, a leg extending from each of said disks, means for clamping said compass card in Xed position with either leg, and means for clamping said disks in any position.

3. A compass ruler comprising an upper circular disk having marks indicating circular divisions, a lower circular disk concentric therewith, said disks being pivoted at their centers, a compass card smaller than the said upper circular disk, superposed thereon and revoluble about said centers, legs having equal divisions marked on the edges thereof extending from said disks, means for clamping said compass card in fixed position with either leg, and means for clamping said disks in any position.

4. A compass ruler comprising an upper circular disk having marks indicating circular divisions, a lower circular disk concentric therewith said disks being pivoted at their centers, a compass card smaller than the said upper circular disk, superposed thereon, and revoluble about said centers, a leg extending from each of said disks, means for clamping said compass card in fixed position, a pointer revoluble about said centers, and means for clamping said disks and said pointer in any position.

In testimony whereof I have set my hand this 16th day of March A. D. 1908, in the presence of the two subscribed witnesses.

JOI-IN ARTHUR RYDMAN. lVitnesses FRANK P. MEDINA, EDITH W. BURNi-IAM. 

